Rotating bed gasifier

ABSTRACT

The present invention includes a gasifier for gasifying fuels having a container with a top, sidewalls and a bottom for facilitating the gasifying process. One or more open vertical shafts extend downward inside the container for allowing a downdraft or updraft of air and fuel for the gasifying process. A rotating bed is preferably included inside the container and below the one or more shafts for receiving the fuel. The bed rotates essentially perpendicular to the shaft to facilitate even heating and gasifying of the fuel.

BACKGROUND OF THE INVENTION

The present invention relates generally to an apparatus for providing a more effective and efficient gasifier apparatus. More particularly, although not exclusively, the present invention relates to a rotating bed gasifier apparatus.

Currently, there are many types of gasifier systems. Typically the gasification process is the primary energy generation means. Gasification generally takes materials, such as wood, coal, charcoal, agricultural residues, energy crops, municipal solid waste or other biomass materials, and gasifies them to make a “gas” used for power or electricity generation or other uses, such as heat production. A typical gasification system consists of a gasifier unit, a filtering system, and an energy converter.

Steam boiler/combustor units are also well-known, though their use for primary energy generation has been questionable for some time, mainly because of the harmful resultant emissions. A steam boiler/combustor creates high pressure steam used for power generation. Prior art systems apply steam boiler/combustor units as secondary energy generation means to gain energy and thus increase efficiency and reduce pollutants such as gasses produced during the gasification process. An example of this type of system can be found in U.S. Pat. No. 6,637,206 to Thiessen, which is herein incorporated by reference in its entirety.

One problem with fixed bed gasifiers is that there are inherent “hot spots” in the fuel, causing uneven gasifying. Some of these systems add moving fingers to the fixed bed to agitate the fuel to aid in the gasification process. The torque force on the fingers increases as the diameter of the fire tube holding the fuel increases. This limits the size of the gasifier which can be constructed. By creating too large a gasifier, these fingers or the shaft holding them bend and break during the agitation.

U.S. Pat. No. 2,226,927 to Rundstrom is an up-draft gasifier which uses a grate system which reciprocates vertically, up and down, within a fixed bed core to maintain an even flow of fuel and gas and allow for the removal of ash. A problem with these vertically reciprocating beds and fixed bed gasifiers is that the larger the gasifier, the more chance for uneven heating inside the gasifier and thus poor gasifying of the fuel.

Thus, in view of the foregoing, it is desirable to have an improved gasifying system that solves these and other problems of the prior art.

Therefore, the primary feature or advantage of the present invention is an improved gasifier.

Another feature or advantage of the present invention is the provision of a gasifier which reduces the size limitations in which a gasifier fuel mixer can be built.

Another feature or advantage of the present invention is the provision of a gasifier that more uniformly heats the material being gasified to improve efficiency.

Another feature or advantage of the present invention is the provision of a gasifier that improves air flow to the fuel.

Another feature or advantage of the present invention is the provision of a gasifier that preferably includes a rotating bed, is economical to manufacture, durable in use and efficient in operation.

These and the other features or advantages of the present invention will be apparent from the specification and claims that follow.

BRIEF SUMMARY OF THE INVENTION

One or more of the foregoing features or advantages may be achieved by a gasifier having a container with a top, sidewalls, and a bottom for facilitating the gasifying process. An open vertical shaft extends down from the top of the container and allows a downdraft or updraft of air to mix with fuel for the gasifying process. A rotating bed inside the container preferably located below the shaft receives the fuel; the bed rotates essentially perpendicular to the shaft.

A further aspect of the present invention involves one or more fingers extending from a lower portion of the shaft for mixing the fuel with the air. The present invention may also include one or more fingers which extend upward from the rotating bed for mixing the fuel with the air. The present invention also preferably includes a shaft attached to the bed for rotating the bed.

Another aspect of the present invention is an ash auger for removing used fuel from the container. Yet another aspect of the present invention is the provision of a gasifier which recycles the used fuel back into the shaft for reusing the fuel. Another provision of the present invention is a gasifier having a bed with sidewalls extending upward to hold the fuel onto the bed.

One or more of the foregoing features or advantages may be achieved by the gasifier having a container with a top, sidewalls, and a bottom for facilitating the gasifying process, a first open vertical shaft extending inside the container, a second open vertical shaft inside the first vertical shaft creating a space between the first and second shafts for allowing a downdraft of air and fuel for the gasifying process in the space between the first and second shafts, and a rotating bed inside the container, below the space between the first and second shafts for receiving the fuel, the bed rotating essentially perpendicular to the shafts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of a gasifier system assembly for using a gasifier to create energy.

FIG. 2 shows a cut away view of one embodiment of a downdraft rotating bed gasifier.

FIG. 2A shows the gasifier of FIG. 2 configured as an updraft gasifier.

FIG. 3 shows a top view of one embodiment of the vertical shaft shown in FIG. 2.

FIG. 4 shows a top view of one embodiment of the rotating trough or bed shown in FIG. 2.

FIG. 5 shows a cut away view of another embodiment of a rotating bed gasifier.

FIG. 6 shows a top view of one embodiment of the rotating bed shown in FIG. 5.

FIG. 7 shows a cut away side view of yet another embodiment of a rotating bed gasifier.

FIG. 8 shows a top view of one embodiment of the rotating bed shown in FIG. 7.

FIG. 9 shows a cutaway view of still another embodiment of a rotating bed gasifier.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a rotating bed gasifier. The present invention can be used in a system such as the system 10 as shown in FIG. 1. However, the present invention can be used in any type of system where a gasifier for gasifying solid fuels is desired.

Referring now to FIG. 2, a cut away side view of one embodiment of a rotating bed gasifier assembly 20 is shown. The gasifier assembly 20 begins with a gasifier container assembly 22. The gasifier container assembly 22 generally has a cylindrical shaped sidewall 24. However, the sidewall 24 can be in any shape. Connected to the sidewall 24 is a top 26 and a bottom 28. Preferably, the bottom 28 is an inverted cone-shaped piece of metal to allow used ashes and overflow fuel or char to fall to a central point of an ash sump 30.

The ash sump 30 is connected to the bottom 28 of the gasifier container assembly 22 preferably is connected to an ash auger 32 for removing the fuel and ashes after they have been through the gasification process and fallen to the bottom of the gasifier assembly 20. The present invention may use an elevator 33 which takes the char or fuel from the auger 32 and recycles it back into the gasifier assembly 20. This allows for the further gasification of the char or fuel and creates a more efficient and more complete gasification of the fuel in the gasifier 20. In addition, less waste ashes have to be removed from the gasifier 20. Therefore, more complete gasification of the fuel is completed. The waste ashes can be separated from the char or fuel by an ash separator 35. The ash separator preferably has a screen 39 for separating the waste ashes from the char or fuel which is to be recycled. Once separated, the ashes can be removed through the ash output 41 and the reusable char or fuel can be sent through the elevator 33.

The gas created by the gasification process in the gasifier assembly 20 extracted from the gasifier 20 through one or more ports 34. The gas can then be used as an energy source for other systems.

Looking now at FIGS. 2 and 3, the gasifier assembly 20 has a vertical shaft 36 which extends through the gasifier container assembly 22 creating a fire tube 37. Preferably, the shaft 36 has one or more fingers 38 extending from a lower portion of the shaft 36. The fingers 38 can extend at any angle from the shaft 36. The fingers 38 allow for breaking up the fuel as it falls down and enters the fire tube 37 and during the gasifying process.

Below the shaft 36 is a rotating trough/bed 40. The rotating bed 40 is attached to a drive shaft 42 which is connected to a sprocket or pulley 44 which is in turn connected to the motor 50 via another sprocket or pulley 52 and a chain or belt 54. There is preferably a bearing (not shown) at the top and the bottom of the drive shaft 42 to facilitate even rotation of the drive shaft 42 and long life. There may also be fingers 43 extending from the drive shaft 42 to aid in mixing the fuel.

The motor 50 is preferably geared down so that the drive shaft 42 and the rotating bed 40 rotate inside the gasifier assembly at approximately one revolution every four minutes. This rotating or revolving bed 40 allows for the solid fuel which rests on the bed 40 and rotates with the bed 40 to revolve, thereby creating more distribution of uniform heat within the circumference of the fire tube 37. This is accomplished by moving the hot spots within the solid fuel around inside the fire tube 37 thereby more uniformly heating the inside of the fire tube 37. In addition, the bed 40 can rotate intermittently and/or reverse directions.

Additionally, it is preferred, but not necessary, that the bed 40 have sidewalls 46 to reduce the amount of fuel falling off the bed 40 before it is thoroughly gasified. In other words, the fuel should remain on the bed 40 until the gasified fuel becomes high enough to fall over the sidewalls 46 and down to the ash sump 30. Furthermore, the bed 40 preferably has one or more fingers 48 extending upward from the bed 40 which allow the rotating bed 40 and the fuel to revolve and mix in a crossing path with the fingers 38 extending from the shaft 36. In other words, the fingers 38, 48 pass one another during revolution of the bed 40 and mix the fuel. This aids in more thorough gasification of the fuel.

As shown in FIG. 4, preferably there are four spaced apart fingers 48 on the bed 40. However, any number of fingers can be used. Preferably, the fingers 48 extend upward at any angle from the bed 40. In addition, the bed 40 can be made from solid sheet metal, perforated metal, expanded metal, or any other material capable of holding the fuel which is to be gasified. With or without holes the rotating bed 40, 78, 120, the ash builds up in the tray and falls over the side and into the gasifier's bottom for removal.

FIG. 2A shows the gasifier assembly 20 configured as an updraft gasifier with the air flow reversed. In this embodiment, the air can enter the port 34, pass through the fuel and exit as a gas upward through the fire tube 37. Other aspects of the gasifier 20 remain the same.

FIGS. 5 and 6 show another embodiment of a gasifier assembly 60. This gasifier assembly 60 operates similar to the gasifier 20 shown in FIG. 2. As shown in FIGS. 5 and 6, the gasifier 60 has a gasifier container 62, with sidewalls 64, top 66 and bottom 68. Preferably, attached to the bottom 68 is an ash sump 70 and an auger 72 for removing the used ashes. In addition, an elevator or other device can be used for recycling the used ashes into the gasifier assembly 60. Again, the gasifier 60 preferably has one or more ports 74 for allowing the gas created in the gasifier 60 to be directed out of the gasifier 60 and used.

In the embodiment shown in FIGS. 5 and 6, the gasifier 60 has a shaft 76 extending downward or vertically into the gasifier container 62 creating a fire tube 77. In the embodiment shown in FIGS. 5 and 6, the gasifier assembly 60 has a rotating trough or bed 78 connected to a drive shaft 80 for revolving the rotating bed 78 similar to that shown in the gasifier assembly 20 of FIGS. 2 and 2A. Support brackets 81 support the bed 78 to the drive shaft 80. There is preferably a bearing (not shown) at the top and the bottom of the drive shaft 80 to facilitate even rotation and long life. Preferably, the drive shaft 80 has a sprocket 82 which connects to a motor assembly 50 for rotating the bed 78. Again, it is preferred that the bed 78 rotates approximately one revolution every four minutes, however other rotations can be used with the present invention. The rotating bed 78 has outside sidewalls 84 to help hold the fuel onto the bed 78. However, the rotating bed 78 has inside sidewalls 86 which extend up into the shaft 76, thereby creating an elongated ring-shaped fire tube 77. This is best shown in FIG. 6. By being constructed in this manner, air can draft downward through the center of the inside sidewalls 86 and enter through optional vents 88 to provide more air for the gasification process. This type of rotating bed 78 also helps to reduce hot and cold spots within the gasifier assembly 60. In addition, the added air coming in through the vents 88 create improved gasification of the fuel. In addition, this gasifier 60 can have updraft air flow.

Still another embodiment of the rotating gasifier assembly 100 is shown in FIGS. 7 and 8. Here again, the gasifier assembly 100 has a gasifier container 102 with sidewalls 104, a top 106, bottom 108, ash sump 110, auger 112, and port 114. The gasifier assembly 100 shown in FIGS. 7 and 8 has a first vertical shaft 116 and a second vertical shaft 118 located concentrically inside the first vertical shaft 116. This creates an elongated ring fire tube 117 as shown in FIG. 8, that is similar to that shown in FIG. 6. However, the second shaft 118 does not rotate with the rotating trough/bed 120. Downdraft air can enter the second vertical shaft 118 and pass through optional vents 119 to enter the fire tube 117 to aid in the gasification of the fuel. The rotating bed 120 is attached to a drive shaft 122 by support brackets 123. There is preferably a bearing (not shown) at both the top and the bottom of the drive shaft 122 to facilitate even rotation and long life. A motor assembly 50 or other similar type driving device is used for creating the revolving motion of the rotating bed 120. It is preferred, that the rotating bed 120 have outside walls 126 and inside walls 128 extending upward from the rotating bed to reduce overflow of the fuel until the gasifying process takes its course.

It is understood that the rotating bed gasifier assemblies 20, 60, 100 can have different shaped or designed rotating beds 40, 78, 120, 142. In addition, the rotating bed 40, 78, 120 can be created with sheet metal, perforated metal, expanded metal, or any other material suitable for holding the fuel which is to be gasified. Furthermore, the rotation of the bed 40, 78, 120, 142 can be any appropriate speed or direction. It is preferred, however that the speed of the rotating bed 40, 78, 120 not be so fast as to reduce or impede the gasifying process.

The preferred fuel for this gasifier is shelled corn. However other fuels can be used. Air is sucked, blown, or both through the fuel which is heated and pyrolyzed, forming gas for the gasification process. The gasification process is self-sustaining with a blower (not shown) operating. The rotating bed 40, 78, 120, 142 replaces the function of a fixed grate in standard gasifiers in the art. The gasification process generally continues until the blower (not shown) or rotating bed 40, 78, 120 stops.

The direction of rotation of the rotating bed 40, 78, 120, 142 can be clockwise or counterclockwise. In addition, the bed 40, 78, 120, 142 can agitate or move intermittently, whatever motion works best for the fuel which is being used. It is preferred that the ring-type rotating troughs 78, 120 are used in place of the pan-type rotating trough 40 once the specifications require the rotating tray to be larger than approximately 36 inches in diameter. This ensures better fuel agitation, which is necessary to overcome the problems of biomass gasification. In addition, ring-type troughs also increases the rate of gasification by substantially increasing the reactive area in the gasifier 20, 60, 100. Rather than restricting the gas flow to the outside of the ring, a ring-type trough may also allow gas to flow across the inside of the ring, as best shown in FIG. 7. In addition to reinforcing the rigidity of the rotating tray 78, 120, the braces or brackets 81, 123 serve to move char/ash to the removal sump 70, 110 where it can be augured out by the auger 72, 112.

The recycling of char back into the fire tube 37, 77, and 117 uses a natural by-product of biomass gasification. Essentially, the char/ash auger 32, 72, 112 is elevated back to the top of the gasifier 20, 60, 100 and reintroduced/recycled by combining it with new solid fuel or biomass fuel which is being fed into the gasifier 20, 60, 100 for the first time. This greatly reduces the amount of ash produced in the process because it gets reused and further reduced each time it is reused.

In addition to biomass fuel, plastic fuel can be combined with biomass fuel to form a fuel blend. Because the plastic is a petrol-chemical derivative, it bums much faster than the biomass fuel. As a result, a filtering effect with this blended fuel can be accomplished by introducing dirty gasses from petrol/fossil fuels which are burned separately in a combustor similar to that as shown as a gasifier system 10 in FIG. 1. Many dirty fuels cannot be blended in this way because of metal which is contained within them. Using dirty fuels with metallic contents would clog the gasifier. Examples of such dirty fuels are tire fluff, medical waste, and circuit boards. However, if the plastics/rubber are homogeneous, blending them with biomass in the proper amount allows their clean burning while increasing the energy output from the gasifier. While any type of fuel can be used within the gasifiers of the present invention, it is noted that petro-chemical derived fuels cannot easily be gasified by themselves. These fuels melt which in turn restricts the necessary air flow and therefore severely limits or stops the gasification process.

It is widely known in the art that coal cannot generally be downdraft gasified easily. Therefore, a gasifier assembly 140 is shown in FIG. 9 as an inverted downdraft gasifier. This gasifier assembly 140 works similar to the previously described gasifiers 20, 60, 100 with a rotating bed assembly 142. This gasifier assembly 140 allows air to flow inward through one or more vents 144, through the fuel, and out through one or more ports 148. This embodiment shows that either a top fuel inlet 150 or a bottom fuel inlet auger 152 can supply fuel into the gasifier 140. The top fuel inlet 150 allows for fuel to enter the gasifier assembly 140 and fall downward into the fire tube 154 for gasification. The bottom fuel inlet auger 152 similarly gets the fuel to the inside of the fire tube 154, however, the bottom fuel inlet auger 152 uses a mechanical auger for feeding the fuel into the fire tube 154. It is preferred that the top input design would not be used if rubber or plastic is mixed with the biomass fuel. In this case, it is preferable that the bottom input design be used for the purpose of combining biomass fuel with petrochemical derived fuels.

It is understood that even though specific references are made to certain parts or sections of the invention in the figures, these specific parts or figures or design styles can be interchanged on any of the gasifiers as may be desired for a specific situation. In other words, any of the features or designs shown or contemplated can be used on any of the contemplated gasifiers.

In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalents are contemplated as circumstance may suggest or render expedient without departing from the spirit or scope of the invention as further defined in the following claims. 

1. A gasifier for gasifying fuels comprising: a container having an inside and an outside; an open air and fuel shaft extending into the inside of the container; and a rotating bed located within the inside of the container, below the air and fuel shaft.
 2. The gasifier of claim 1 further comprising one or more fingers extending from a lower portion of the fuel shaft.
 3. The gasifier of claim 1 further comprising one or more fingers extending upward from the rotating bed.
 4. The gasifier of claim 1 further comprising a drive shaft attached to the bed for rotating the bed.
 5. The gasifier of claim 4 further comprising one or more fingers extending outward from the drive shaft.
 6. The gasifier of claim 1 further comprising an ash auger to remove used fuel from the container.
 7. The gasifier of claim 1 further comprising an elevator that recycles used fuel back into the fuel shaft.
 8. The gasifier of claim 1 wherein the rotating bed has sidewalls extending upwardly.
 9. A gasifier for gasifying fuels comprising: a container with a top, sidewalls, and a bottom; a first open shaft extending down inside the container; a second shaft inside the first shaft creating a space between the first and second shafts for allowing a draft of air and fuel for gasifying the fuels; and a rotating bed inside the container, below the space between the first and second shafts for receiving the fuel.
 10. The gasifier of claim 9 wherein one of the shafts rotates with the bed.
 11. The gasifier of claim 9 further comprising one or more air vents through a sidewall of the first and/or second shaft allowing air to travel through the first and/or second shaft and to enter the space between the first and second shaft to aid in the gasifying process.
 12. The gasifier of claim 9 further comprising an ash sump and a device for recycling the fuel back through the gasifier.
 13. The gasifier of claim 12 wherein the device for recycling the fuel is an auger.
 14. The gasifier of claim 9 wherein the bed has sidewalls extending upward to help hold the fuel onto the bed.
 15. The gasifier of claim 9 further comprising one or more fingers extending from a lower portion of the first and/or second shaft for mixing the fuel.
 16. The gasifier of claim 9 further comprising one or more fingers extending upward from the rotating bed for mixing the fuel.
 17. The gasifier of claim 9 further comprising a drive shaft attached to the bed for rotating the bed.
 18. The gasifier of claim 9 further comprising one or more fingers extending from the drive shaft for mixing the fuel.
 19. A method of gasifying biomass fuel comprising: inserting biomass fuel into a fire tube of a gasifier; supplying heat and air to the fuel; and stirring the fuel to promote uniform gasification of the fuel.
 20. The method of claim 19 wherein the stirring of the fuel is by rotating a bed which is supporting the fuel.
 21. The method of claim 20 wherein the bed rotation is about ¼ revolution per minute.
 22. The method of claim 19 further comprising recycling fuel into the fire tube. 